1. Field of the Invention
The present invention relates to a sealing apparatus and lubrication system for rotating shafts and, more particularly, to a stern tube seal and lubrication system for a propeller shaft of a ship.
2. Background Information
Systems of this type, which are disclosed in German Laid Open Patent Application No. 3122406, work satisfactorily if the liquid medium, such as lubricating oil, against which a seal is to be made does not have an extremely low temperature when the shaft is restarted after a rather long shutdown. That is because if the temperature is not extremely low, then the viscosity of the lubricating oil does not increase as much during shutdown of the shaft as when the temperature is extremely low. However, when the shaft resumes operation under extremely low temperature conditions, the seal gaskets, which generally consist of rubber or elastic material, may become damaged and their sealing function or capability may, thus, be reduced.
The same, or similar, conditions exist if water is used as a lubricant, because no ice is formed on the gaskets unless extremely low temperatures are encountered. However, if conditions prevail in which the water is severely supercooled, as is the case in icy waters and oceans, the sealing devices no longer work satisfactorily because the water in the annular chamber of the seal freezes. Also, under such supercooled conditions, if lubricating oil is used, the lubricating oil becomes highly viscous in the relatively small annular seal chambers. In both cases, the danger then exists that the gaskets will be damaged, particularly on their sealing edges, and thus their sealing function may be adversely affected or even destroyed.